Probiotics are favorable microorganisms that regulate the flora of the gastrointestinal system and stimulate the immune system. Necrotizing enterocolitis incidence is 10-25% in newborn infants whose birth weights are < 1500 gr. Although bifidobacterium and lactobacilli sp. have been used to reduce the incidence of NEC in clinical trials, Saccharomyces boulardii has not been used in the prevention of NEC in very low birth weight infants yet. The objective of this study is to evaluate the efficacy of orally administered S boulardii in reducing the incidence and severity of NEC in very low birth weight infants.